Various structures have been proposed for window lifter systems having a winding drum, a geared motor unit operatively coupled to the drum to turn the drum, and a drum casing that accommodates the drum. A seal is often used to hold the drum in the drum casing, but it is difficult to obtain an effective seal without adversely affecting drum rotation.
European Patent EP-B-0 892 724 discloses a sheet metal door with openings. A plastic winding drum turns inside a drum casing and is lodged between the sheet metal and the casing. The drum casing is fastened to the drum with a resilient clip fastener. The sheet metal has a bore through which the fastener is inserted. The geared motor unit and its associated motor unit casing is disposed on the sheet metal and attached to the drum so that the sheet metal is sandwiched between the drum casing and the motor unit casing. The motor unit casing is fixed to the drum casing with a screw housed in the resilient clip fastener.
Likewise, U.S. Pat. No. 6,152,646 discloses a support plate supporting a geared motor unit casing and a drum casing on either side of the support plate. The geared motor unit casing is fixed to the drum casing with a screw passing through the casings.
The devices described above have several disadvantages, however. On the one hand, the structures described above do not provide secure sealing between the two faces of the sheet metal or adequate support at the juncture between the geared motor unit and drum casings. Secure sealing is particularly important to protect the electrical and electronic components of the geared motor unit from moisture. On the other hand, currently known structures do not align the drum correctly in the drum casing before the drum casing is fastened to the sheet metal, potentially causing the drum to deviate from its optimal position within the casing.
One way to optimize drum positioning within the casing is to form a seal that contacts the drum to hold the drum in place. DE-A-19 812 875 discloses a window lifter with a drum casing and a seal where the seal is urged against a lateral surface of the drum. The seal provides a sealing function and also holds the drum on its axis of rotation via frictional contact. However, the friction between the drum and the seal causes conflict between providing a secure seal between the drum and the seal and holding the drum to prevent translation of the drum along its rotational axis. Furthermore, the friction between the seal and the drum tends to deteriorate the seal, degrading both the sealing power and the translational holding power of the seal against the drum.
U.S. Pat. No. 4,503,732 discloses a window lifter drum mounted to turn inside a box. The faces of the drum each have a seal that is integrally formed with the drum to provide a seal between the drum and the box. Although the integral seal does provide tight sealing, it also impedes free rotation of the drum within the box.
International Application WO-A-97 43 564 discloses a geared motor unit for a window lifter. The geared motor unit includes a seal that contacts a toothed wheel driven by the geared motor unit. The seal slides against an interior annular wall of the toothed wheel.
There is therefore a need for a device and a method of assembly which solve one or more of the disadvantages of currently known structures.